Posts Tagged ‘mobile operation’
Handiham World for 16 May 2012
Welcome to Handiham World.
You can do it!
Today, just as we did last week, we are going to begin with Troubleshooting 101 as part of our initiative to help new ham radio operators (and even some of us older ones) learn how to do some basic troubleshooting for ourselves. Yes, it can be tempting to ask someone else to do things for us. This can become a bad habit when it keeps us from learning new things, especially things that we could – with a bit of practice – learn to do for ourselves. Knowing these basic things can serve us well in the future when no help is available.
Let’s get to today’s troubleshooting question:
I sometimes use my handheld radio in the car. I can hear the repeater just fine, but I have had complaints that other stations can’t hear me. What’s going on here? Is there something wrong with my HT?
Yes, I’m afraid there is a problem with your radio. The problem is that it has a terrible antenna. Before you complain that the radio has always worked quite well when you used it around the house, let me explain.
Handheld radios are meant to be portable so that they are easy to carry around. Haven’t you noticed that people prefer smaller, lighter electronic devices? So what was once referred to as “a brick” – the venerable 2 meter HT – has evolved to a multiband miniaturized wonder that fits in the palm of your hand. The antenna on the old brink was just about the same length as the one on your new radio, though. These flexible “rubber duck” antennas are the ones that come as standard equipment with a new handheld radio. They have always been terrible antennas, but they are designed to be flexible so that they can bend without breaking and generally survive being dumped into a backpack, stuffed into a pocket, or crammed into a purse. A quarter-wave antenna for the 2 meter band should be around 19 inches long (48 cm), but the radio would hardly be portable with that big antenna, would it? The rubber duck antenna is inductively loaded so that it can be physically shorter but still act like an electrical quarter wave.
This seems like a great solution because now you have the equivalent of 19 inches of antenna in a tiny, convenient flexible stick. Ha, ha, that is a good one. Most of these rubber antennas are more like a “dummy load on a stick”. They are inefficient and lossy. A rubber antenna that came with the HT is probably okay if you are in a good location and not far from the repeater and are not moving around. The rubber antenna can receive okay but is not going to win any awards, but transmitting efficiently is just plain not a happening thing. When you move the antenna around, every slight cancellation of signal from multipath reception becomes a near-dropout. It is even worse inside a car, where the body of the car can block part of the signal and you are nearly always moving. No wonder your friends are complaining about your signal – because it is terrible!
I placed my tiny Yaesu VX5R HT with the somewhat bent from years of carrying it in my pocket next to an old Larson 1/4 wavelength magnet mount antenna. The ACTUAL quarter wave mag mount towers over the HT with its wimpy rubber antenna. If only there were a way to use a quarter-wave magnet mount antenna, or even a 5/8 wavelength mag mount antenna, with my HT it would sure solve my transmitting problem and make the HT more useful as a temporary mobile radio.
Of course there is a way; you just need to get the right adapter to mate the mag mount antenna’s connector to your HT and you are in business, right?
Well, no – it’s not quite that easy. For one thing, you might not have a mag mount antenna. And you may not be familiar with these kinds of temporary antennas, especially if you are not a driver yourself and you ride with a spouse or a friend. Here are some things to consider:
- If you are going to move the antenna around a lot, such as using it on a friend’s car then removing it after you get where you are going, there are tiny, highly-portable miniature mag mount antennas with small diameter coax (RG-174U) with a connector to fit directly onto your HT. Actually, I prefer these antennas over other mag mounts because the light, flexible coax will not put extra stress on your radio’s SMA connector. MFJ makes the MFJ-1722 dual-band mag mount antenna and it is only around $15 – an accessory to your HT that is well worth the money.
- If you already have a more conventional larger mag mount with RG-58 coax, I recommend an adapter with a short piece of RG-174U coax so that the flexibility of the cable allows for comfortably moving the HT about as you use it. Stiff coax will put excessive pressure on the HT’s antenna connector and may eventually break it.
- If you are using an HT with an SMA connector, you may want to consider a special connector adaptor that seats against the body of the radio, taking pressure off the antenna connector.
- Pay attention to the routing of the feedline out the door. It may run through the gap between the door and the car’s frame, but choose a spot where the rubber gasket around the door frame will close gently against the wire.
- Avoid sharp bends when running coax.
- For longer term installations, test the water seal around the coax entry point with a garden hose.
- Place the antenna on the roof of the vehicle or on the deck of the trunk lid if the cable is to be run through the back seat and out into the trunk.
- Be sure the magnet has a serious grip on the metal car body!
- Avoid long, flapping runs of wire across the roof or trunk.
- If you have an antenna that screws onto a magnetic base, be sure it is screwed on tightly before traveling!
- Consider a small, easy to remove antenna that is placed just outside and above a back door. You can easily grab it off the roof and shove it on the back seat floor under a mat when you want to conceal the fact that you have a radio in the car or if you need the extra clearance to get into the garage. While you’re at it, unhook the HT and put it in the glove box or take it with you.
- If you are serious about using an HT in the car, you might also pop for the optional car charger. All the HT manufacturers offer them, and they can be in the glove box with an extra rubber duck antenna when not in use. You will likely need high power while operating mobile, and that can run your battery down quickly.
Once you start using a “real” antenna mounted outside the vehicle, you will wonder how you ever got by with an HT and the rubber antenna.
Email me at [email protected] with your questions & comments.
Patrick Tice, WA0TDA